Exploration of the crystal structures and electronic features of Y2O3:Er and Y2O3:Er,Yb crystals: a first-principles study

The Er3+ doped Y2O3 (Y2O3:Er) and Er3+, Yb3+ co-doped Y2O3 (Y2O3:Er,Yb) have attracted considerable attention due to their outstanding optical properties. However, the crystal structures underlying their electronic features are still unclear. In this paper, we carried out the systematical structural evolutions of Y2O3:Er and Y2O3:Er,Yb via the Crystal Structural AnaLYsis by Particle Swarm Optimization structure search method. Two novel monoclinic structures with P2 space group were uncovered for Y2O3:Er and Y2O3:Er,Yb. Validities of the two ground state structures were verified by the good agreements between the calculated x-ray diffraction patterns and the experimental ones. Phonon dispersion curves were also investigated, and the data showed that the ground state structures of both Y2O3:Er and Y2O3:Er,Yb were dynamically stable. Moreover, the density of states, the band structure and the electronic local function of these two systems were also studied. The impurity Er3+ and Yb3+ ions lead to the transition of electronic feature from the insulator to the semiconductor. The Y-O, Er-O, Yb-O bonds are proved to be covalent bonds. These research results can fill up the vacancy and give instructions in the rare-earth doped laser materials in the future.